Rockhopper Regulatory News (RKH)

9 April 2015

Rockhopper Exploration plc

 ("Rockhopper" or the "Company")

14/20-1 Well Spud 'Isobel Deep'

Rockhopper Exploration plc (AIM: RKH), the oil and gas exploration and production company with interests in the North Falkland Basin and the Greater Mediterranean region, announces that the 14/20-1 'Isobel Deep' well (the "Well") was spudded, by Premier Oil as operator, at 22:20 local time on the 8th April 2015.

The Well is located on licence PL004a in which Rockhopper has a 24% working interest and is an exploration well on the Isobel deep prospect. The Isobel Deep Well will be the first test of the F3 fan system entering the basin from the South East margin as a sequence of stacked reservoirs. This well will be targeting the Isobel deep fan in the area of maximum mapped reservoir thickness and has a GCoS of 20%. The well is targeting Gross Pmean resources of 72mmbbls (range 9-207mmbbls) although the complex as a whole in this area has gross Pmean prospective resources of just over 500mmbbls.

Drilling operations are expected to take approximately 30 days and no coring or testing is planned for this well. A further release will be made when drilling is completed.

The North Falkland Basin wells are anticipated to cost approximately US$50 million each. As a result of the various carry arrangements, the total net cash exposure to Rockhopper of the four wells is estimated at approximately US$25 million.

Samuel Moody, CEO, commented:

"We are delighted to be spudding the second well of the campaign following the successful Zebedee oil and gas discovery. The Isobel Deep Well is a high risk high impact well which has the potential in the success case to open a new development area."

For further information, please contact:

Rockhopper Exploration plc

Tel: (via Vigo Communications) - 020 7016 9571

Sam Moody - Chief Executive

Fiona MacAulay - Chief Operating Officer

Stewart MacDonald - Chief Financial Officer

Canaccord Genuity Limited (NOMAD and Joint Broker)

Tel: 020 7523 8000

Henry Fitzgerald-O'Connor

Liberum Capital (Joint Broker)

Tel: 020 3100 2227

Clayton Bush

Vigo Communications

Peter Reilly 020 7016 9571

Patrick d'Ancona 020 7016 9573

Note regarding Rockhopper oil and gas disclosure

This announcement has been approved by Rockhopper's geological staff who include Fiona MacAulay (Chief Operating Officer), who is a Fellow of the Geological Society of London and a Member of the Petroleum Exploration Society of Great Britain and American Association of Petroleum Geologists with over 25 years of experience in petroleum exploration and management, and who is the qualified person as defined in the Guidance Note for Mining, Oil and Gas Companies issued by the London Stock Exchange in respect of AIM companies. In compiling its resource estimates, Rockhopper has used the definitions and guidelines as set forth in the 2007 Petroleum Resources Management System approved by the Society of Petroleum Engineers.

GCoS Geological Chance of Success

Pmean : Average (mean) probability of occurrence

Prospective Resource : the resource estimated to exist in prospect areas considered viable to drill, but which have not yet been proven by drilling